1. Field of the Invention
The present invention relates generally to portable terminals including cellular phone, digital phone, PDA (Personal Digital Assistant), and HHP (Hand-Held Phone), and in particular, to a backlighting device for a dual Liquid Crystal Display (LCD) and a folder-type mobile phone therewith.
2. Description of the Related Art
In general, as more and more personal mobile communication services are introduced, services employing mobile telephones are quite diversified, and accordingly, designs and functions of the mobile phone are rapidly changing. In particular, the latest folder-type mobile phone has two Liquid Crystal Displays (LCDs), one mounted on the inside on an inner surface of a folder and another mounted on the outside on an outer surface of the folder so that a user can conveniently check simple information or status information of the mobile phone through the LCD mounted on the outer surface of the folder without opening the folder.
FIG. 1A is a perspective view of a folder-type mobile phone on which a typical dual LCD is mounted, and FIG. 1B is a perspective view showing a folded state of the folder-type mobile phone illustrated in FIG. 1A. As illustrated in FIG. 1A, a typical folder-type mobile phone 100 includes a body 110 and a folder 160 rotatably connected to the body 110 by an undepicted hinge. The body 110 includes a mouthpiece 120 with a microphone, and a keypad 130 comprised of a key matrix for inputting. The folder 160 is comprised of a main LCD 170 facing the body 110, and an earpiece 180 with a built-in speaker (not shown). Further, as illustrated in FIG. 1B, the folder 160 has a slave LCD 190 mounted on an outer surface thereof. The main LCD 170 and the slave LCD 190, constituting a dual-LCD display device of the mobile phone 100, display a telephone number being dialed, status information of the mobile phone 100, and a variety of other information set by the user. The slave LCD 190 can also display simple information such as date, time, battery status indication icon, antenna reception sensitivity icon, etc.
FIG. 2 is a cross sectional view illustrating a structure of a known LCD used as the main LCD and the slave LCD illustrated in FIGS. 1A and 1B. As illustrated in FIG. 2, a known LCD 200 has liquid crystal 210, an upper glass 230, and a lower glass 250. The upper and lower glasses 230 and 250 are attached on upper and lower faces of the liquid crystal 210, respectively. An upper polarizer 270 is attached on the upper glass 230 and a lower polarizer 290 is attached on the lower glass 250. As the LCD 200 is controlled by an LCD driver (not illustrated herein), the user can visually identify displayed information. In addition, a backlighting device is provided to enable the user to view a variety of information displayed on the LCD in dark places or at night.
FIG. 3 is a cross sectional view of a dual LCD for a mobile phone with two separate backlighting devices according to the prior art. As illustrated in FIG. 3, a conventional dual LCD 300 with backlighting devices 320 and 330 has a main LCD 311 installed on one face of a circuit board 301 and a slave LCD 313 installed on another face. The backlighting devices 320 and 330 are constructed between the main LCD 311 and the circuit board 301 and between the slave LCD 313 and the circuit board 301, respectively, in the same manner.
The backlighting device 320 has a diffusion sheet 321 attached on a lower face of the main LCD 311, a light guide plate 323 attached on a lower face of the diffusion sheet 321, and a reflection plate 325 attached on a lower face of the light guide plate 323, the reflection plate 325 being coupled with the circuit board 301. In addition, a light emitting diode (LED) 327 is installed adjacent to the light guide plate 323, and the light emitted by the LED 327 is flashed on the main LCD 311. Light generated at the LED 327 is transferred to the light guide plate 323, reflected by the reflection plate 325, and transferred to the main LCD 311. The light transferred to the main LCD 311 is evenly diffused across the main LCD 311 by the diffusion sheet 321. A white, blue, or red light emitting diode can be used for the LED 327.
The backlighting device 330 of the slave LCD 313 is constructed in the same manner as the backlighting device 320 of the main LCD 311. Accordingly, construction of the backlighting device 330 of the slave LCD 313 needs not be elaborated herein, for simplicity.
FIG. 4 is a cross sectional view of another dual LCD for a mobile phone with two separate backlighting devices according to the prior art. As illustrated in FIG. 4, a conventional dual LCD 400 with backlighting devices 420 and 430 has a main LCD 411 installed on one face of a circuit board 401 and a slave LCD 413 on another face of the circuit board 401, and the backlighting devices 420 and 430 are constructed between the main LCD 411 and the circuit board 401 and between the slave LCD 413 and the circuit board 401, respectively, in the same manner.
The backlighting device 420 has a diffusion sheet 421 attached at the lower part of the main LCD 411, an electro-luminescence (EL) sheet 423 attached at the lower part of the diffusion sheet 421, and a reflection sheet 425 attached at the lower part of the EL sheet 423, the reflection sheet 425 being coupled with the circuit board 401. Further, being an active light-emitting element, the electro-luminescence sheet 423 generates light for illuminating the main LCD 411, and the light emitted by the electro-luminescence sheet 423 flashes on the main LCD 411. Light generated at the electro-luminescence sheet 423 is reflected by the reflection sheet 425 and transferred to the main LCD 411. Here, the light transferred to the main LCD 411 is evenly diffused across the whole surface of the main LCD 411 by the diffusion sheet 421.
The backlighting device 430 for the slave LCD 413 is constructed in the same manner as the backlighting device 420 of the main LCD 411. Accordingly, construction of the backlighting device 430 of the slave LCD 412 needs not be elaborated herein, for simplicity.
A backlighting device for a dual LCD may be constructed by combining the backlighting device using the light emitting diode as a light source with the backlighting device using the electro-luminescence sheet as a light source.
In the foregoing examples, the backlighting device requires installation of light emitting diode or electro-luminescence sheet as a light source, diffusion sheet, and reflection plate both in the main LCD and the slave LCD separately in a symmetric manner, giving a serious limitation in making the mobile phone compact and especially, slim.
Specifically, the dual LCD is applied mainly to folder-type mobile phones, so the backlighting devices with the same construction have to be separately installed in both the main LCD and the slave LCD, making the folder thicker. In addition, when using different light sources for main LCD and slave LCD, for example, when using the electro-luminescence sheet as a light source for the main LCD and the light emitting diode as a light source for the slave LCD, a control circuit for controlling the light sources needs to be separately constructed, making the control circuit complicated and impeding compactness of the mobile phone.